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test_all_project_files() in test_lib2to3 emits warnings in verbose mode.
/home/serhiy/py/cpython/Lib/lib2to3/tests/test_parser.py:415: UserWarning: ParseError on file /home/serhiy/py/cpython/Lib/lib2to3/main.py (bad input: type=22, value='=', context=('', (130, 38)))
 warnings.warn('ParseError on file %s (%s)' % (filepath, err))
/home/serhiy/py/cpython/Lib/lib2to3/tests/test_parser.py:415: UserWarning: ParseError on file /home/serhiy/py/cpython/Lib/lib2to3/tests/pytree_idempotency.py (bad input: type=22, value='=', context=('', (49, 33)))
 warnings.warn('ParseError on file %s (%s)' % (filepath, err))
ParseError is raised by lines like:
 print("Use --help to show usage.", file=sys.stderr)
Seems "from __future__ import print_function" doesn't work.

The warnings were introduced with issue13125 and this was fixed with issue30117 . I verified it as below : 
➜ cpython git:(master) git checkout 14e976e00e65bf343ba0fca016c3c9132a843daf~1
➜ cpython git:(ce0f33d045) git clean -xdf && ./configure --with-pydebug && make -s -j4
➜ cpython git:(ce0f33d045) time ./python.exe -I -S -m test.regrtest -vv test_import test_lib2to3 >/dev/null
Warning -- files was modified by test_import
 Before: []
 After: ['@test_41673_tmp.pyc']
/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/lib2to3/tests/test_parser.py:430: UserWarning: ParseError on file /Users/karthikeyansingaravelan/stuff/python/cpython/Lib/lib2to3/main.py (bad input: type=22, value='=', context=('', (130, 38)))
 warnings.warn('ParseError on file %s (%s)' % (filepath, err))
/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/lib2to3/tests/test_parser.py:430: UserWarning: ParseError on file /Users/karthikeyansingaravelan/stuff/python/cpython/Lib/lib2to3/tests/pytree_idempotency.py (bad input: type=22, value='=', context=('', (49, 33)))
 warnings.warn('ParseError on file %s (%s)' % (filepath, err))
./python.exe -I -S -m test.regrtest -vv test_import test_lib2to3 > /dev/null 44.31s user 1.18s system 94% cpu 47.971 total
# Fixed commit
➜ cpython git:(14e976e00e) time ./python.exe -I -S -m test.regrtest -vv test_import test_lib2to3 >/dev/null
Warning -- files was modified by test_import
 Before: []
 After: ['@test_41839_tmp.pyc']
./python.exe -I -S -m test.regrtest -vv test_import test_lib2to3 > /dev/null 50.50s user 1.56s system 91% cpu 56.778 total
The test_import warning is also not reproducible with master as of now I will find the necessary commit and reply back in issue28655. As part of triaging I am closing this as duplicate with issue30117 as superseder which has the fix. Feel free to reopen this if needed.
Thanks

Thanks Karthikeyan!